The secret life of bookmarks

A bonus of buying secondhand books is finding the previous owner's markings in the text and folded corners as bookmarks. Or in this case, a postcard memory of the Hotel Bauer Grunwald, with no name or date. When I first read it I thought it said "Remember choix outside!", as in "choice" but I think it says "chox" as in chocolates. First glance was better.